Next, Working Group 3 has evaluated and analysed current pass/fail criteria for helmet testing, and discovered a number of antiquated or inadequate parameters for these tests. In an extensive evaluation, the Working Group has examined head injury criteria at a number of different levels. These include an evaluation of existing head injury criteria, as well as a review of specific head injury criteria based on:
- Translational acceleration;
- Rotational acceleration and velocity;
- Combined rotational and translational acceleration;
- Finite Element (FE) Head Model-based head injury criteria;
The group also introduced advanced head models, which enable the computation of axon strain at the time of impact. The simulation of 115 real-world head trauma incidents were used to define initial limits for model-specific based brain injury criteria, as well as post-processing tools for end-users. Finally, a coupled experimental versus numerical test method was defined.
Illustration of the coupled experimental versus numerical head impact test method based on head FE modelling
After the evaluations were complete, the Working Group reached the conclusion that it is possible to use both global pass/fail criteria, such as BRIC, RIC, HIP or PrHIC, or to use the more advanced, model-based pass/fail criteria that were developed within the group. Both methods, however, do need further work in order to be tuned to a final pass/fail criteria used in a helmet test standard.